Salt suitable for an acid generator and a chemically amplified resist composition containing the same

ABSTRACT

The present invention provides a salt of the formula (I): 
                         
wherein ring X represents polycyclic hydrocarbon group having tricycle or more and having 10 to 30 carbon atoms, and one or more hydrogen atom in the ring X is optionally substituted with alkyl group having 1 to 6 carbon atoms, alkoxy group having 1 to 6 carbon atoms, perfluoroalkyl group having 1 to 4 carbon atoms or cyano group; Q 1  and Q 2  each independently represent fluorine atom or perfluoroalkyl group having 1 to 6 carbon atoms; n shows an integer of 1 to 12; and A +  represents a cation selected from the group consist of a cation of the following formulae (IIa), (IIb) and (IIc):
 
     
       
         
         
             
             
         
       
     
     The present invention also provides a chemically amplified resist composition comprising the salt of the formula (I).

This nonprovisional application claims priority under 35 U.S.C § 119(a) on Patent Application No. 2005-314036 filed in JAPAN on Oct. 28, 2005, the entire contents of which are hereby incorporated by reference.

FIELD OF THE INVENTION

The present invention relates to a salt suitable for an acid generator used for a chemical amplification type resist which is used in fine processing of semiconductors, and a chemically amplified resist composition containing the salt.

BACKGROUND OF THE INVENTION

A chemically amplified resist composition used for semiconductor microfabrication employing a lithography process contains an acid generator comprising a compound generating an acid by irradiation.

In semiconductor microfabrication, it is desirable to form patterns having improved line edge roughness and excellent pattern shape, and it is expected for a chemically amplified resist composition to give such patterns. Hereinafter, “line edge roughness” can be abbreviated to “LER”.

Recently, a chemically amplified resist composition containing triphenylsulfonium 1-adamantanemethoxycarbonyldifluoromethansulfonate, p-tolyldiphenylsulfonium perfluorooctanesulfonate, and the like are proposed (e.g. JP2004-4561-A), and a salt providing a chemically amplified resist composition giving patterns having improved line edge roughness and excellent pattern shape.

SUMMARY OF THE INVENTION

Objects of the present invention are to provide a salt suitable for an acid generator capable of providing chemically amplified resist compositions giving patterns having improved line edge roughness and excellent pattern shape.

Another object of the present invention are to provide synthetic intermediates for the salts and to provide a process for producing the synthetic intermediates or the salts.

Still another object of the present invention are to provide a chemically amplified resist composition containing the salts.

These and other objects of the present invention will be apparent from the following description.

The present invention relates to the followings:

-   <1> A salt of the formula (I):

-   -   wherein ring X represents polycyclic hydrocarbon group having         tricycle or more and having 10 to 30 carbon atoms, and one or         more hydrogen atom in the ring X is optionally substituted with         alkyl group having 1 to 6 carbon atoms, alkoxy group having 1 to         6 carbon atoms, perfluoroalkyl group having 1 to 4 carbon atoms         or cyano groups; Q¹ and Q² each independently represent fluorine         atom or perfluoroalkyl group having 1 to 6 carbon atoms; n shows         an integer of 1 to 12; and A⁺ represents a cation selected from         the group consisting of a cation of the following formulae         (IIa), (IIb) and (IIc): a cation of the formula (IIa):

-   -   wherein P¹ and P² each independently represent hydrogen atom,         hydroxyl group, alkyl group having 1 to 12 carbon atoms or         alkoxy group having 1 to 12 carbon atoms, a cation of the         formula (IIb):

-   -   wherein P³ and P⁴ each independently represent alkyl group         having 1 to 12 carbon atoms or cycloalkyl group having 3 to 12         carbon atoms, or P³ and P⁴ bond to form divalent acyclic         hydrocarbon group having 3 to 12 carbon atoms which forms a ring         together with the adjacent S⁺, and one or more —CH₂— in the         divalent acyclic hydrocarbon group is optionally substituted         with —CO—, —O— or —S—, P⁵ represents hydrogen atom, P⁶         represents alkyl group having 1 to 12 carbon atoms, cycloalkyl         group having 3 to 12 carbon atoms or aromatic ring group         optionally substituted, or P⁵ and P⁶ bond to form divalent         acyclic hydrocarbon group which forms 2-oxocycloalkyl together         with the adjacent —CHCO—, and one or more —CH₂— in the divalent         acyclic hydrocarbon group is optionally substituted with —CO—,         —O— or —S—,         a cation of the formula (IIc):

-   -   wherein P⁷,P⁸,P⁹,P¹⁰,P¹¹,P¹²,P¹³,P¹⁴,P¹⁵,P¹⁶,P¹⁷ and P¹⁸ each         independently represent hydrogen atom, hydroxyl group, alkyl         group having 1 to 12 carbon atoms or alkoxy group having 1 to 12         carbon atoms, B represents sulfur atom or oxygen atom, and m         shows 0 or 1. Hereinafter, the salt of the formula (I) may also         be referred to as Salt (I).

-   <2> The salt according to <1>, wherein each of Q¹ and Q² is     independently fluorine atom or trifluoromethyl group.

-   <3> The salt according to <1> or <2>, wherein the ring X is     tricyclic, tetracyclic, pentacyclic or hexacyclic hydrocarbon groups     having 10 to 20 carbon atoms.

-   <4> The salt according to any of <1> to <3>, wherein the ring X is     monovalent residue of a compound shown by the formula (IIIa) or     (IIIb):

-   -   wherein X¹ represents (a) alkylene group or (b) oxygen atom, X²         represents (a) alkylene group, (b) oxygen atom or (c) no bonding         and hydrogen atom in each side, and one or more hydrogen atom in         the formulae (IIIa) and (IIIb) is optionally substituted with         alkyl group having 1 to 6 carbon atoms, alkoxy group having 1 to         6 carbon atoms, perfluoroalkyl group having 1 to 4 carbon atoms         or cyano group.

-   <5> The salt according to any of <1> to <4>, wherein A⁺ is a cation     of the formula (IId)

-   -   wherein P¹⁹ and P²⁰ each independently represent alkyl group         having 1 to 6 carbon atoms or cycloalkyl group having 3 to 6         carbon atoms, or P¹⁹ and P²⁰ bond to form divalent acyclic         hydrocarbon group having 3 to 6 carbon atoms which forms a ring         together with the adjacent S⁺, and one or more —CH₂— in the         divalent acyclic hydrocarbon group is optionally substituted         with —CO—, —O— or —S—, P²¹ represents hydrogen atom, P²²         represents alkyl group having 1 to 6 carbon atoms, cycloalkyl         group having 3 to 6 carbon atoms or aromatic ring group         optionally substituted, or P²¹ and P²² bond to form divalent         acyclic hydrocarbon group which forms 2-oxocycloalkyl together         with the adjacent —CHCO—, and one or more —CH₂— in the divalent         acyclic hydrocarbon group is optionally substituted with —CO—,         —O— or —S—,.

-   <6> The salt according to <1>, wherein the salt is the one of the     formula (IV)

-   -   wherein P¹⁹,P²⁰,P²¹ and P²² have the same meanings as defined         above:

-   <7> An ester compound of the formula (V)

-   -   wherein X represents polycyclic hydrocarbon group having         tricycle or more and having 10 to 30 carbon atoms, and one or         more hydrogen atom in the ring X is optionally substituted with         alkyl group having 1 to 6 carbon atoms, alkoxy group having 1 to         6 carbon atoms, perfluoroalkyl group having 1 to 4 carbon atoms         or cyano group; Q¹ and Q² each independently represent fluorine         atom or perfluoroalkyl group having 1 to 6 carbon atoms; n shows         1 or 2; and M represents Li, Na, K or Ag.

-   <8> The ester compound according to <7>, wherein each of Q¹ and Q²     is independently fluorine atom or trifluoromethyl group.

-   <9> A process for producing an ester compound of the formula (V),     which comprises reacting an alcohol compound of the formula (VI)

-   -   wherein the ring X and n have the same meanings as defined         above, with a carboxylic acid compound of the formula (VII)

-   -   wherein M, Q¹ and Q² have the same meanings as defined above.

-   <10> A Process for producing Salt (I), which comprises reacting an     ester compound of the formula (V) with a compound of the formula     (VIII)     A⁺ Z⁻  (VIII)     -   wherein Z represents F, Cl, Br, I, BF₄, Asf₆, SbF₆, PF₆ or ClO₄,         and A⁺ has the same meaning as defined above.

-   <11> A chemically amplified resist composition comprising     Salt (I) and     a resin which contains a structural unit having an acid-labile group     and which itself is insoluble or poorly soluble in an alkali aqueous     solution but becomes soluble in an alkali aqueous solution by the     action of an acid.

-   <12> The composition according to <11>, wherein the resin contains a     structural unit derived from a monomer having a bulky and     acid-labile group.

-   <13> The composition according to <12>, wherein the bulky and     acid-labile group is 2-alkyl-2adamantyl group or     1-(1-adamantyl)-1-alkylalkyl group.

-   <14> The composition according to <12>, wherein the monomer having     bulky and acid-labile group is 2-alkyl-2-adamantyl (meth)acrylate,     1-(1-adamantyl)-1-alkylalkyl (meth)acrylate, 2-alkyl-2-adamantyl     5-norbornene-2-carboxylate, 1-(1-adamantyl)-1-alkylalkyl     5-norbornene-2-carboxylate, 2-alkyl-2-adamantyl α-chloroacrylate or     1-(1-adamantyl)-1-alkylalkyl α-chloroacrylate.

-   <15> The composition according to any of <11>, wherein the     composition further comprises a basic compound.

-   <16> The composition according to any of <11> to <15>, wherein each     of Q¹ and Q² is independently fluorine atom or trifluoromethyl     group.

-   <17> The composition according to any of <11> to <16>, wherein the     ring X is tricyclic, tetracyclic, pentacyclic or hexacyclic     hydrocarbon groups having 10 to 20 carbon atoms.

-   <18> The composition according to any of <11> to <17>, wherein the     ring X is monovalent residue of a compound shown by the formula     (IIIa) or (IIIb).

-   <19> The composition according to any of <11> to <18>, wherein A⁺ is     a cation of the formula (IId).

-   <20> The composition according to any of <11> to <15>, wherein the     salt is the one of the formula (IV).

DESCRIPTION OF PREFERRED EMBODIMENTS

The present invention provides Salt (I).

The ring X in the formulae (I), (V) and (VI) represents polycyclic hydrocarbon group having tricycle or more and the polycyclic hydrocarbon group has 6 to 30, preferably 10 to 30 carbon atoms. One or more hydrogen atom in the ring X is optionally substituted with alkyl group having 1 to 6 carbon atoms, alkoxy group having 1 to 6 carbon atoms, perfluoroalkyl group having 1 to 4 carbon atoms or cyano group.

It is preferred that the ring X is tricyclic hydrocarbon group, tetracyclic hydrocarbon group, pentacyclic hydrocarbon group or hexacyclic hydrocarbon group having 10 to 20 carbon atoms. One or more hydrogen atom in the tricyclic hydrocarbon group, tetracyclic hydrocarbon group, pentacyclic hydrocarbon group or hexacyclic hydrocarbon group is optionally substituted with alkyl group having 1 to 6 carbon atoms, alkoxy group having 1 to 6 carbon atoms, perfluoroalkyl group having 1 to 4 carbon atoms or cyano group.

More preferred examples of the ring X include monovalent residue of a compound shown by the formula (IIIa) or (IIIb).

X¹ represents (a) alkylene group such as methylene group and ethylene group or (b) oxygen atom (—O—). X² represents (a) alkylene group such as methylene group and ethylene group, (b) oxygen atom (—O—) or (c) no bonding and hydrogen atom in each side.

Specific examples of the compound of the formulae (IIIa) and (IIIb) include the following:

“n” is 1 to 6, and preferably 1 to 2.

Q¹ and Q² each independently represent fluorine atom or perfluoroalkyl group having 1 to 6 carbon atoms such as trifluoromethyl group, pentafluoroethyl group, heptafluoropropyl group, nonafluorobutyl group, undecafluoropentyl group, tridecafluorohexyl group, and the like. As Q¹ and Q², fluorine atom and trifuoromethyl group are preferred.

Specific examples of anion part of the Salt (I) include the followings.

A⁺ in the formulae (I) and (VIII) represents a cation of the formula (IIa), the formula (IIb) or the formula (IIc),

In the cation of the formula (IIa), P¹ and P¹ each independently represent hydrogen atom, hydroxyl group, alkyl group having 1 to 12 carbon atoms or alkoxy group having 1 to 12 carbon atoms. Examples of the alkyl group in the formula (IIa) include methyl group, ethyl group, propyl group, isopropyl group, n-butyl group, sec-butyl group, tert-butyl group, pentyl group, hexyl group, octyl group, 2ethylhexyl group, and the like, and examples of the alkoxy group include methoxy group, ethoxy group, propoxy group, butoxy group, hexyloxy group, octyloxy group, 2-ethylhexyloxy group, and the like

In the cation of the formula (IIb), P³ and P⁴ each independently represent alkyl group having 1 to 12 carbon atoms or cycloalkyl group having 3 to 12 carbon atoms, or P³ and P⁴ bond to form divalent acyclic hydrocarbon group having 3 to 12 carbon atoms which forms a ring together with the adjacent S⁺, and one or more —CH₂— in the divalent acyclic hydrocarbon group may be substituted with —CO—, —O— or —S—.

P⁵ represents hydrogen, P⁶ represents alkyl group having 1 to 12 carbon atoms, cycloalkyl group having 3 to 12 carbon atoms or aromatic ring group optionally substituted, or P⁵ and P⁶ bond to form divalent acyclic hydrocarbon group which forms 2-oxocycloalkyl group together with the adjacent —CHCO—, and one or more —CH₂— in the divalent acyclic hydrocarbon group is optionally substituted with —CO—, —O— or —S—.

In P³, P⁴ and P⁶, specific examples of the alkyl group include methyl group, ethyl group, propyl group, isopropyl group, butyl group, tert-butyl group, pentyl group, hexyl group, Octyl group, 2-ethylhexyl group, and the like, and specific examples of the cycloalkyl group include cyclopropyl group, cyclobutyl group, cyclopentyl group, cyclohexyl group, cycloheptyl group, cyclodecyl group, and the like. Specific examples of the divalent acyclic hydrocarbon group having 3 to 12 carbon atoms formed by bonding P³ and P⁴ include trimethylene group, tetramethylene group, pentaethylene group, and the like, and specific examples of the ring group formed by adjacent S⁺ and divalent acyclic hydrocarbon group by P³ and P⁴ include pentamethylenesulfonio group, tetramethylenesulfonio group, oxybisethylenesulfonio group, and the like. In P⁶, specific examples of the aromatic ring group include phenyl, tolyl, xylyl, naphtyl and the like. Specific examples of the divalent acylic hydrocarbon group formed by bonding P⁵ and P⁶ include methylene group, ethylene group, trimethylene group, tetramethylene group, pentamethylene group, and the like, and specific examples of the 2-oxocycloalkyl formed by bonding P⁵ and P⁶ together with the adjacent —CHCO— include 2-oxocyclohexyl, 2-oxocyclopentyl and the like.

In the cation of the formula (IIc), P⁷, P⁸, P⁹, P¹⁰, P¹¹, P¹², P¹³, P¹⁴, P¹⁵, P¹⁶, P¹⁷ and P¹⁸ each independently represent hydrogen atom, hydroxyl group, alkyl group having 1 to 12 carbon atoms or alkoxy group having 1 to 12 carbon atoms, B represents sulfur atom or oxygen atom, and m represents 0 or 1. Examples of the alkyl group and alkoxy group include the same groups as mentioned in the cation of the formula (IIa) above.

Specific examples of the cation of the formula (IIa) include the following:

Specific examples of the cation of the formula (IIb) include the following:

Specific examples of the cation of the formula (IIc) include the following:

As Salt (I), the salt of the formula (IV) is preferred for providing chemically amplified resist compositions giving patents having more improved line edge roughness and more excellent pattern shape.

Examples of a process for production of Salt (I) include a process comprising reacting an ester of the formula (V) with an onium salt of the formula (VIII), in an inert solvent such as acetonitrile, water, methanol, chloroform and dichloromethane at a temperature of 0 to 150° C., preferably of 0 to 100° C.

The amount of the oniun salt of the formula (VII) is usually 0.5 to 2 mol per 1 mol of the ester of the formula (V). Salt (I) obtained can be taken out by recrystallization when it is in crystal form or by extraction by solvents and concentration when it is in oil form.

Examples of a process for production of the ester of the formula (V) include a process reacting an alcohol compound of the formula (VI) with a carboxylic acid compound of the formula (VII).

The esterfication reaction can generally be carried out by mixing materials in an aprotic solvent such as dichloroethane, toluene, ethylbenzene, monochlorobenzene, acetonitrile, N,N-dimethylformamide, and the like, at 20 to 200° C., preferably 50 to 150° C. In the esterification reaction, an acid catalyst or a dehydrating agent is usually added, and examples of the acid catalyst include organic acids such as p-toluenesulfonic acid, inorganic acids such as sulfuric acid, and the like. Examples of the dehydrating agent include 1,1′-carbonyldiimidazole, N,N′-dicyclohexylcarbodiimide, and the like.

The esterifcation may preferably be carried out with dehydration, for example, by Dean and Stark method as the reaction time tends to be shortened.

The amount of the carboxylic acid compound of the formula (VII) is usually 0.2 to 3 mol, preferably 0.5 to 2 mol per 1 mol of the alcohol compound of the formula (VI). The amount of the acid catalyst may be catalytic amount or the amount equivalent to solvent, and is usually 0.001 to 5 mol per 1 mol of the alcohol compound of the formula (VI). The amount of the dehydrating agent is usually 0.2 to 5 mol preferably 0.5 to 3 mol per 1 mol of the alcohol compound of the formula (VI).

The present chemically amplified resist composition comprises Salt (I) and a resin which contains a structural unit having an acid-labile group and which itself is insoluble or poorly soluble in an alkali aqueous solution but becomes soluble in an alkali aqueous solution by the action of an acid

Salt (I) is usually used as an acid generator, and the acid generated by irradiation to Salt (I) catalytically acts against acid-labile groups in a resin, cleaves the acid-labile-group, and the resin becomes soluble in an alkali aqueous solution. Such a composition is suitable for chemically amplified positive resist composition.

The resin used for the present composition contains a structural unit having an acid-labile group and which itself is insoluble or poorly soluble in an alkali aqueous solution, but acid-labile group cleave by an acid. The resin after the cleavage contains carboxylic acid residue and as a result, the resin becomes soluble in an alkali aqueous solution.

In the present specification, “—COOR” may be described as “a structure having ester of carboxylic acid”, and may also be abbreviated as “ester group”. Specifically, “—COOC(CH₃)₃” may be described as “a structure having tert-butyl ester of carboxylic acid”, or be abbreviated as “tert-butyl ester group”.

Examples of the acid-labile group include a structure having ester of carboxylic acid such as alkyl ester group in which a carbon atom adjacent to the oxygen atom is quaternary carbon atom, and alicyclic ester group in which a carbon atom adjacent to the oxygen atom is quaternary carbon atom, and the like, a lactone ring group in which a carbon atom adjacent to the oxygen atom is quaternary carbon atom, and the like.

The “quaternary carbon atom” means a “carbon atom joined to four substituents other than hydrogen atom”.

Examples of the acid-labile group include alkyl ester group in which a carbon atom adjacent to the oxygen atom is quaternary carbon atom such as tert-butyl ester group; acetal type ester group such as methoxymethyl ester group, ethoxymethyl ester group, 1-ethoxyethyl ester group, 1-isobutoxyethyl ester group, 1-isopropoxyethyl ester group, 1-ethoxypropyl ester group, 1-(2-methoxyethoxy)ethyl ester, 1-(2-acetoxyethoxy)ethyl ester group, 1-[2-(1-adamantyloxy)ethoxy]ethyl ester group, 1-[2-(1-adamantanecarbonyloxy)ethoxy]ethyl ester group, tetrahydro-2-furyl ester and tetrahydro-2-pyranyl ester group; alicyclic ester group in which a carbon atom adjacent to the oxygen atom is quaternary carbon atom, such as isobornyl ester group, 1-alkylcycloalkyl ester group, 2-alkyl-2-adamantyl ester group, 1-(1-adamantyl)-1-alkylalkyl ester group, and the like.

Examples of structures including the ester group include ester of (meth)acrylic acid structure, ester of norbornenecarboxylic acid structure, ester of tricyclodecenecarboxylic acid structure, tetracyclodecenecarboxylic acid structure, and the like. At least one hydrogen atom in the adamantyl group above may be substituted by hydroxyl group.

The resin used for the present composition can be obtained by addition polymerization of monomer(s) having an acid-labile group and olefinic double bond,

Among the monomers, it is preferable to use those having a bulky group such as alicyclic group (e.g. 2alkyl-2-adamantyl and 1-(1-adamantyl)-1-alkylalkyl), as the group dissociated by the action of an acid, since excellent resolution is obtained when used in the present composition.

Examples of such monomer containing a bulky group include 2alkyl-2adamantyl (meth)acrylate, 1-(1-adamantyl-1-alkylalkyl (meth)acrylate, 2-alkyl-2-adamantyl 5-norbornene-2-carboxylate, 1-(1-adamantyl)-1-alkylalkyl 5-norbornene-2-carboxylate, 2-alkyl-2adamantyl α-chloroacrylate, 1-(1-adamantyl)-1-alkylalkyl α-chloroacrylate and the like.

Particularly when 2-alkyl-23-adamantyl (meth)acrylate or 2-alkyl-2-adamantyl α-chloroacrylate is used as the monomer for the resin component in the present composition, resist composition having excellent resolution tend to be obtained. Typical examples of such 2-alkyl-2adamantyl (meth)acrylate and 2-alkyl-2-adamantyl α-chloroacrylate include 2-methyl-2-adamantyl acrylate, 2-methyl-2-adamantyl methacrylate, 2-ethyl-2-adamantyl acrylate, 2-ethyl-2-adamantyl methacrylate, 2-n-butyl-2-adamantyl acrylate, 2-methyl-2-adamantyl α-chloroacrylate, 2-ethyl-2-adamantyl α-chloroacrylate and the like. When particularly 2-ethyl-2adamantyl (meth)acrylate or 2-isopropyl-2-adamantyl (meth)acrylate is used for the present composition, composition having excellent sensitivity and heat resistance tends to be obtained. In the present invention, two or more kind of monomers having group dissociated by the action of an acid may be used together, if necessary

2-Alkyl-2-adamantyl (meth)acrylate can usually be produced by reacting 2-alkyl-2-adamantanol or metal salt hereof with an acrylic halide or methacrylic halide.

The resin used for the present composition can also contain, in addition to the above-mentioned structural units having an acid-labile group, other structural unit derived from acid-stable monomer. Herein, the “structural unit derived from acid-stable monomer” means “a structural unit not dissociated by an acid generated from Salt (I)”.

Examples of such other structural units which can be contained include structural units derived from monomers having a free carboxyl group such as acrylic acid and methacrylic acid, structural units derived from aliphatic unsaturated dicarboxylic anhydrides such as maleic anhydride and itaconic anhydride, structural units derived from 2-norbornene, structural units derived from (meth)acrylonitrile, structural units derived from alkyl (meth)acrylate in which a carbon atom adjacent to oxygen atom is secondary or tertiary carbon atom, structural units derived from 1-adamantyl (meth)acrylate, structural units derived from styrenes such as p- or m-hydroxystyrene, structural units derived from (meth)acryloyloxy-γ-butyrolactone having a lactone ring optionally substituted by alkyl and the like. Herein, 1-adamantyl ester group is a acid-stable group though the carbon atom adjacent to oxygen atom is a quaternary carbon atom, and at least one hydrogen atom on 1-adamanty ester group may be substituted by hydroxy group.

Specific examples of structural unit derived from acid-stable monomer include a structural unit derived from 3-hydroxyl-1-adamantyl (meth)acrylate, a structural unit derived from 3,5-dihydroxy-1-adamantyl (meth)acrylate, a structural unit derived from α-(meth)acryloyloxy-γ-butyrolactone, a structural unit derived from β-(meth)acryloyloxy-γ-butyrolactone, a structural unit of the following formula (a), a structural unit derived from the following formula (b), a structural unit derived from alicyclic compound having olefinic double bond such as a structural unit of the following formula (c), a structural unit derived from aliphatic unsaturated dicarboxylic anhydride such as a structural unit of the formula (d), a structural unit of the formula (e), and the like.

Particularly, to contain, in addition to the structural unit having an acid-labile group, further at least one structural unit selected from the group consisting of a structural unit derived from p-hydroxystyrene, a structural unit derived from m-hydroxystyrene, a structural unit derived from 3-hydroxy-1-adamantyl (meth)acrylate, a structural unit derived from 3,5-dihydroxy-1-adamantyl(meth)acrylate, a structural unit of the following formula (a) and a structural unit of the following formula (b), in the resin in the present composition, is preferable from the standpoint of the adhesiveness of resist to a substrate and resolution of resist.

In the formulae (a) and (b), R¹ and R² each independently represent hydrogen atom, methyl group or trifluoromethyl group and R³ and R⁴ each independently represent methyl group, trifluoromethyl group or halogen atom, and p and q each independently represent an integer of 0 to 3. When p represents 2 or 3, each of the R³ may be the same or different and when q represents 2 or 3, each of the R⁴ may be the same or different.

3Hydroxy-1-adamantyl (meth)acrylate and 3,5-dihydroxy-1-adamantyl (meth)acrylate can be produced, for example, by reacting corresponding hydroxyadamantane with (meth)acrylic acid or its acid halide, and they are also commercially available.

Further, (meth)acryloyloxy-γ-butyrolactone having a lactone ring optionally substituted by alkyl can be produced by reacting corresponding α- or β-bromo-γ-butyrolactone with acrylic acid or methacrylic acid, or reacting corresponding α- or β-hydroxy-γ-butyrolactone with acrylic halide or methacrylic halide.

As monomers to give structural units of the formulae (a) and (b), specifically listed are, for example, (meth)acrylates of alicyclic lactones having hydroxyl described below, and mixtures thereof, and the like. These esters can be produced, for example, by reacting corresponding alicyclic lactone having hydroxyl with (meth)acrylic acids, and the production method thereof is described in, for example, JP2000-26446-A.

Examples of the (meth)acryloyloxy-γ-butyrolactone having a lactone ring optionally substituted by alkyl include α-acryloyloxy-γ-butyrolactone, α-methacryloyloxy-γ-butyrolactone, α-acryloyloxy-β,β-dimethyl-γ-butyrolactone, α-methacryloyloxy-β,β-dimethyl-γ-butyrolactone, α-acryloyloxy-α-methyl-γ-butyrolactone, α-methacryloyloxy-α-methyl-γ-butyrolactone, β-acryloyloxy-γ-butyrolactone, β-methacryloyloxy-γ-butyrolactone, β-methacryloyloxy-α-methyl-γ-butyrolactone and the like.

In the case of KrF lithography, even in the case of using a structure unit derived from hydroxystyrene such as p- and m-hydroxystyrene, as one of the resin components, resist composition having sufficient transparency can be obtained. For obtaining such copolymerization resins, the corresponding (meth)acrylic ester monomer can be radical-polymerized with acetoxystyrene and styrene, and then the acetoxy group in the structure unit derived from acetoxystyrene can be de-acetylated with an acid.

The resin containing a structural unit derived from 2-norbornene shows strong structure because alicyclic group is directly present on its main chain and shows a property that dry etching resistance is excellent. The structural unit derived from 2-norbornene can be introduced into the main chain by radical polymerization using, for example, in addition to corresponding 2-norbornene, aliphatic unsaturated dicarboxylic anhydrides such as maleic anhydride and itaconic anhydride together. The structural unit derived from 2-norbornene is formed by opening of its double bond, and can be represented by the formula (c). The structural unit derived from maleic anhydride and the structural unit derived from itaconic anhydride which are the structural unit derived from aliphatic unsaturated dicarboxylic anhydrides are formed by opening of their double bonds, and can be represented by the formula (d) and the formula (e) respectively.

Here, R⁵ and R⁶ in the formula (c) each independently represent hydrogen, alkyl having 1 to 3 carbon atoms, hydroxyalkyl having 1 to 3 carbon atoms, carboxyl, cyano or —COOU group in which U represents alcohol residue, or R⁵ and R⁶ can bond together to form a carboxylic anhydride residue represented by —C(═O)OC(═O)—.

In R¹ and R⁶, examples of the alkyl include methyl ethyl, propyl and isopropyl, specific examples of hydroxyalkyl include hydroxymethyl, 2-hydroxyethyl and the like.

In R⁵ and R⁶, —COOU group is an ester formed from carboxyl and as the alcohol residue corresponding to U, for example, optionally substituted alkyls having about 1 to 8 carbon atoms, 2-oxooxolan-3- or -4-yl and the like are listed, and as the substituent on the alkyl, hydroxyl, alicyclic hydrocarbon residues and the like are listed.

Specific examples of the monomer used to give the structural unit represented by the formula (c) may include the followings;

2-norbornene,

2-hydroxy-5-norbornene,

5-norbornen-2-carboxylic acid,

methyl 5-norbornen-2-carboxylate,

2-hydroxyethyl 5-norbornen-2-carboxylate,

5-norbornen-2-methanol,

5-norbornen-2, 3-dicarboxylic acid anhydride, and the like.

When U in —COOU is acid-labile group, the structural unit of the formula (c) is a structural unit having acid-labile group even if it has norbornene structure. Examples of monomers giving structural unit having acid-labile group include t-butyl 5-norbornen-2-carboxylate, 1-cyclohexyl-1-methylethyl 5-norbornen-2carboxylate, 1-methylcyclohexyl 5-norbornen-2-carboxylate, 2-methyl-2-adamantyl 5 -norbornen-2-carboxylate, 2-ethyl-2-adamantyl 5-norbornen-2-carboxylate, 1-(4-methylcyclohexyl)-1-methylethyl 5-norbornen-2-carboxylate, 1(4-hydroxylcyclohexyl)-1-methylethyl 5-nobornen-2-carboxylate, 1-methyl-1-(4-oxocyclohexyl)ethyl 5-norbornen-2-carboxylate, 1-(1-adamantyl)-1-methylethyl 5-norbornen-2-carboxylate, and the like.

The resin used in the present composition preferably contains structural unit(s) having an acid-labile group generally in a ratio of 10 to 80% by mol in all structural units of the resin though the ratio varies depending on the kind of radiation for patterning exposure, the kind of an acid-labile group, and the like.

When the structural units particularly derived from 2-alkyl-2-adamantyl (meth)acrylate or 1-(1-adamantyl)-1-alkylalkyl (meth)acrylate are used as the acid-labile group, it is advantageous in dry-etching resistance of the resist that the ratio of the structural units is 15% by mol or more in all structural units of the resin.

When, in addition to structural units having an acid-labile group, other structural units having acid-stable group are contained, it is preferable that the sum of these structural units is in the range of 20 to 90% by mol based on all structural units of the resin.

When alicyclic compound having olefinic double bond and aliphatic unsaturated dicarboxylic anhydride are used as copolymerization monomer, it is preferable to use them in excess amount in view of a tendency that these are not easily polymerized.

In the present composition, performance deterioration caused by inactivation of acid which occurs due to post exposure delay can be diminished by adding basic compounds, particularly, basic nitrogen-containing organic compounds, for example, amines as a quencher.

Specific examples of such basic nitrogen-containing organic compounds include the ones represented by the following formulae:

In the formulas, T¹² and T¹³ each independently represent a hydrogen atom, an alkyl group, a cycloalkyl group or an aryl group. The alkyl group preferably has about 1 to 6 carbon atoms, the cycloalkyl group preferably has about 5 to 10 carbon atoms, and the aryl group preferably has about 6 to 10 carbon atoms. Furthermore, at least one hydrogen atom on the alkyl group, cycloalkyl group or aryl group may each independently be substituted with hydroxyl group, amino group, or alkoxy group having 1 to 6 carbon atoms. At least one hydrogen atom on the amino group may each independently be substituted with alkyl group having 1 to 4 carbon atoms.

T¹⁴, T¹⁵ and T¹⁶ each independently represent a hydrogen atom, an alkyl group, a cycloalkyl group, an aryl group or an alkoxy group. The allyl group preferably has about 1 to 6 carbon atoms, the cycloalkyl group preferably has about 5 to 10 carbon atoms, the alkyl group preferably has about 6 to 10 carbon atoms, and the alkoxy group preferably has about 1 to 6 carbon atoms. Furthermore, at least one hydrogen atom on the alkyl group, cycloalkyl group, aryl group or alkoxy group may each independently be substituted with hydroxyl group, amino group, or alkaxy group having 1 to 6 carbon atoms. At least one hydrogen atom on the amino group may be substituted with alkyl group having 1 to 4 carbon atoms.

T¹⁷ represents an alkyl group or a cycloakyl group. The alkyl group preferably has about 1 to 6 carbon atoms, and the cycloalkyl group preferably has about 5 to 10 carbon atoms. Furthermore, at least one hydrogen atom on the allyl group or cycloalkyl group may each independently be substituted with hydroxyl group, amino group, or alkoxy group having 1 to 6 carbon atoms. At least one hydrogen atom on the amino group may be substituted with alkyl group having 1 to 4 carbon atoms.

In the formulas, T¹⁸ represents an alkyl group, a cycloalkyl group or an aryl group. The alkyl group preferably has about 1 to 6 carbon atoms, the cycloalkyl group preferably has about 5 to 10 carbon atoms, and the aryl group preferably has about 6 to 10 carbon atoms. Furthermore, at least one hydrogen atom on the alkyl group, cycloalkyl group or aryl group nay each independently be substituted with a hydroxyl group, an amino group, or an alkoxy group having 1 to 6 carbon atoms. At least one hydrogen atom on the amino group may each independently be substituted with alkyl group having 1 to 4 carbon atoms.

However, none of T¹² and T¹³ in the compound represented by the above formula [3] is a hydrogen atom.

A represents alkylene group, carbonyl group, imino group, sulfide group or disulfide group. The alkylene group preferably has about 2 to 6 carbon atoms.

Moreover, among T¹²-T¹³, in regard to those which can be straight-chained or branched, either of these may be permitted.

T¹⁹, T²⁰ and T²¹ each independently represent a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an aminalkyl group having 1 to 6 carbon atoms, a hydroxyalkyl group having 1 to 6 carbon atoms or a substituted or unsubstituted aryl group having 6 to 20 carbon atoms, or T¹⁹ and T²⁰ bond to form an alkylene group which forms a lactam ring together with adjacent —CO—N—.

Examples of such compounds include hexylamine, heptylamine, octylamine, nonylamine, decylamine, aniline, 2-, 3- or 4-methylaniline, ethylenediamine, tetramethylenediamine, hexamethylenediamine, 4,4′-diamino-1,2-diphenylethane, 4,4′-diamino-3,3′-dimethyldiphenylmethane, 4,4′-diamino-3,3′-diethyldiphenylmethane, dibutylamine, dipentylamine, dihexylamine, diheptylamine, dioctylamine, dioctylamine, dinonylamine, didecylamine, N-methylaniline, piperidine, diphenylamine, triethylamine, trimethylamine, tripropylamine, tributylamine, tripentylamine, trihexylamine, triheptylamine, trioctylamine, trinonylamine, tridecylamine, methyldibutylamine, methyldipentylamine, methyldihexylamine, methyldicyclohexylamine, methyldiheptylamine, methyldioctylamine, methyldinonylamine, methyldidecylamine, ethyldibutylamine, ethydipentylamine, ethyldihexylamine, ethydiheptylamine, ethyldioctylamine, ethyldinonylamine, ethyldidecylamine, dicyclohexylmethylamine, tris[2-(2-methoxyethoxy)ethyl]amine, triisopropanolamine, N,N-dimethylaniline, 2,6-isopropylaniline, pyridine, 4-methylpyridine, bipyridine, 2,2′-dipyridylamine, di-2-pyridylketone, 1,2-di(2-pyridyl)ethane, 1,2-di(4-pyridyl)ethane, 1,3-di(4-pyridyl)propane, 1,2-bis(2-pyridyl)ethylene, 1,2-bis(4-pyridyl)ethylene, 4,4′-dipyridyl sulfide, 4,4′-dipyridyl disulfide, 1,2-bis(4-pyridyl)ethylene, 2,2′-dipicolylamine, 3,3′-dipicolylamine, tetramethylammonium hydroxide, tetraisopropylammonium hydroxide, tetrabutylammonium hydroxide, tetra-n-hexylammonium hydroxide, tetra-n-octylammonium hydroxide, phenyltrimethylammonium hydroxide, 3-trifluoromethylphenyltrimethylammonium hydroxide, (2-hydroxyethyl)trimethylammonium hydroxide (so-called “choline”), N-methylpyrrolidone, and the like.

Furthermore, hindered amine compounds having piperidine skeleton as disclosed in JP-A-H11-52575 can be used as quencher.

It is preferable that the present composition contain resin component in an amount of about 80 to 99.9% by weight and Salt (I) in an amount of 0.1 to 20% by weight on the total amount of the resin component and Salt (I).

When basic compound is used as a quencher, the basic compound is contained preferably in an amount of about 0.01 to 5 parts, more preferably in an amount of about 0.01 to 1 part by weight per 100 parts by weight of sum of resin component and Salt (I).

The present composition can contain, if necessary, various additives in small amount such as a sensitizer, solution suppressing agent, other polymers, surfactant, stabilizer, dye and the like, as long as the effect of the present invention is not prevented.

The present composition is usually in the form of a resist liquid composition in which the aforementioned ingredients are dissolved in a solvent, and the resist liquid composition is to be applied onto a substrate such as a silicon wafer by a conventional process such as spin coating. The solvent used here is sufficient to dissolve the aforementioned ingredients, have an adequate drying rate, and give a uniform and smooth coat after evaporation of the solvent and, hence, solvents generally used in the art can be used. In the present invention, the total solid content means total content exclusive of solvents.

Examples thereof include glycol ether esters such as ethyl Cellosolve acetate, methyl Cellosolve acetate and propylene glycol monomethyl ether acetate; glycol ethers such as propylene glycol monomethyl ether, di(ethylene glycol) dimethyl ether; esters such as ethyl lactate, butyl lactate, amyl lactate and ethyl pyruvate and the like; ketones such as acetone, methyl isobutyl ketone, 2-heptanone and cyclohexanone; cyclic esters such as γ-butyrolactone, and the like. These solvents can be used each alone or in combination of two or more.

A resist film applied onto the substrate and then dried is subjected to exposure for patterning, then heat-treated for facilitating a deblocking reaction, and thereafter developed with an alkali developer. The alkali developer used here may be any one of various alkaline aqueous solutions used in the art, and generally, an aqueous solution of tetramethylammonium hydroxide or (2-hydroxymethyl)trimethylammonium hydroxide (commonly known as “choline”) is often used.

It should be construed that embodiments disclosed here are examples in all aspects and not restrictive. It is intended that the scope of the present invention is determined not by the above descriptions but by appended Claims, and includes all variations of the equivalent meanings and ranges to the Claims.

The present invention will be described more specifically by way of examples, which are not construed to limit the scope of the present invention. The “%” and “part(s)” used to represent the content of any component and the amount of any material used in the following examples and comparative examples are on a weight basis unless otherwise specifically noted. The weight-average molecular weight of any material used in the following examples is a value found by gel permeation chromatography [HLC-8120GPC Type, Column (Three Columns): TSKgel Multipore HXL-M, Solvent: Tetrahydrofuran, manufactured by TOSOH CORPORATION] using styrene as a standard reference material. Structures of compounds were determined by NMR (GX-270 Type, or EX-270 Type, manufactured by JEOL LTD) and mass spectrometry (Liquid Chromatography: 1100 Type, manufactured by Agilient, Mass Spectrometry: LC/MSD Type or LCD/MSD TOF Type, manufactured by Agilient).

EXAMPLE 1 (Synthesis of 1-(3,3dimethyl-2oxobutyl)tetrahydrothiophenium 1-adamantylmethoxycarbonyldifluoromethanesulfonate)

(1) 460 Parts of 30% aqueous sodium hydroxide solution was added dropwise into a mixture of 200 parts of methyl difluoro(fluorosulfonyl)acetate and 300 parts of ion-exchanged water in a ice bath. The added mixture was heated and refluxed at 100° C. for 2.5 hours. After cooling, the cooled mixture was neutralized with 175 parts of conc. hydrochloric acid and concentrated to obtain 328.19 parts of sodium difluorosulfoacetate (containing inorganic salt, purity: 62.8%).

(2) 123.3 Parts of sodium difluorosulfoacetate (purity: 62.8%), 65.7 parts of 1-adamantanemethanol and 600 parts of dichloroethane were charged in a vessel, 75.1 parts of p-toluenesulfonic acid (p-TsOH) was added thereto, and the mixture was refluxed for 12 hours. After concentrating the mixture to eliminate dichloroethane, 400 parts of acetonitrile was added thereto to wash, and the washing solvent was eliminated by filtration. The solid obtained by filtration was added with 400 parts of acetonitrile and the mixture was stirred and filtrated. The addition of acetonitrile, stirring and filtration were repeated one more time. The filtrate was concentrated to obtain 99.5 parts of sodium salt of 1-adamantylmethyl difluorosulfoacetate.

¹H-NMR data (dimethylsulfoxide-d₆, Internal Standard: tetramethylsilane): d(ppm) 1.51 (d, 6H); 1.62 (dd, 6H); 1.92 (s, 3H); 3.80 (s,2H)

(3) 70.2 Parts of tetrahydrothiophene was dissolved in 750 parts of acetone, and 150 parts of 1-bromo-3,3-dimethyl-2-butanone was added dropwise thereto. After the mixture was stirred at room temperature for 24 hours, white solid obtained was filtered, washed with acetone and dried to obtain 161.3 parts of 1-(3,3-dimethyl-2-oxobutyl)tetrahydrothiophenium bromide in the form of white crystals.

¹HMR data (dimethylsulfoxide-d₆, Internal Standard: tetramethylsilane): d(ppm) 1.14 (s, 9H); 208-2.30 (m, 4H); 3.37-3.58 (m, 4H); 5.03 (s, 2H)

(4) 5.0 Parts of sodium salt of 1-adamantylmethyl difluorosulfoacetate obtained in (2) above was dissolved in 50 parts of ion-exchanged water. A solution consisting of 3.86 parts of 1(3,3-dimethyl-2-oxobutyl)tetrahydrothiophenium bromide obtained in (3) above and 19.3 parts of ion-exchanged water was added to the solution and then 50 parts of acetonitrile was further added thereto to make a completely dissolved solution. After stirred for 15 hours, the stirred mixture was concentrated and extracted with 100 parts of chloroform twice. The organic layers were mixed and washed with ion-exchanged water. The obtained organic layer was concentrated. 100 Parts of tert-butyl methyl ether was added to the concentrate, and the mixture was stirred, filtered and dried in reduced pressure obtain 4.93 parts of 1-(3,3-dimethyl-2-oxobutyl)tetrahydrothiophenium 1-adamantylmethoxycarbonyldifluoromethanesulfonate in the form of white crystals, which is called as acid generator B1.

¹H-NMR data of acid generator B1 (dimethylsulfoxide-d₆, Internal Standard; tetramethylsilane): d(ppm) 1.15 (s, 9H), 152 (d, 6H); 1.63 (dd, 6H); 1.93 (s, 3H); 2.01-2.30 (m, 4H); 3.28-356 (m, 4H); 3.82 (s, 2H); 4.85 (s, 2H) MS (ESI(+) Spectrum): M+187.2(C₁₀H₁₉OS⁺=187.12) MS (ESI(−) Spectrum): M−323.0 (C₁₃H₁₇F₂O₅S⁻=323.08)

EXAMPLE 2 (Synthesis of 1-(2-oxo-2-phenylethyl)tetrahydrothiophenium 1-adamantylmethoxycarbonyldifluoromethanesulfonate)

(1) 150 Parts of 2-bromoacetophenone was dissolved in 375 parts of acetone, and 66.5 parts of tetrahydrothiophene was added dropwise thereto. After the mixture was stirred at room temperature for 24 hours, white solid obtained was filtered, washed with acetone and then dried to obtain 207.9 parts of 1-(2-oxo-2-phenylethyl)tetrahydrothiophenium bromide in the form of white crystals.

¹H-NMR data (dimethylsulfoxide-d₆, Internal Standard tetramethylsilane): d(ppm) 2.13-2.36 (m, 4H); 3.50-3.67 (m, 4H); 5.41 (s, 2H) 7.63 (t, 2H); 7.78 (t, 1H); 8.02 (d, 2H)

(2) 99.5 Parts of sodium salt of sodium salt of 1-adamantylmethyl difluorosulfoacetate obtained in Example 1 (2) was dissolved in 298 parts of acetonitrile. A solution consisting of 79.5 parts of 1-(2-oxo-2-phenylethyl)tetrahydrothiophenium bromide obtained in (1) above and 159 parts of ion-exchanged water was added to the solution. After stirred for 15 hours, the stirred mixture was concentrated and extracted with 500 parts of chloroform twice. The organic layers were mixed and washed with ion exchanged water. The obtained organic layer was concentrated. 250 Parts of tert-butyl methyl ether was added to the concentrate, and the mixture was stirred, filtered and dried in reduced pressure obtain 116.9 parts of 1-(2-oxo-2-phenylethyl)tetrahydrothiophenium 1-adamantylmethoxycarbonyldifluoromethanesulfonate in the form of white crystals, which is called as acid generator B2.

¹H-NMR data of acid generator B1 (dimethylsulfoxide-d₆, Internal Standard: tetramethylsilane): d(ppm) 1.50 (d, 6H); 1.62 (dd, 6H); 1.92 (s, 3H); 2.13-2.32 (m, 4H); 3.45-3.63 (m, 4H); 3.80 (s, 2H); 5.30 (s, 2H); 7.62 (t, 2H); 7.76 (t, 1H); 8.00 (d, 2H) MS (ESI(+) Spectrum): M+207.0 (C₁₂H₁₅OS⁺=207.08) MS (ESI(−) Spectrum):M-323.0 (C₁₃ H₁₇F₂O₅S⁻=323.08)

EXAMPLE 3 (Synthesis of 1-(2-oxo-2-(4′-methylphenylethyl))tetydrothiophenium 1-adamantylmethoxycarbonyldifluoromethanesulfonate)

(1) 50 Parts of 2-bromo-4′-methylacetophenone was dissolved in 1.50 parts of acetone, then 21 parts of tetrahydrothiophene was added dropwise thereto. After stirred at room temperature for 24 hours, white solid obtained was filtered, washed with acetone and dried to obtain 65 parts of 1-(2oxo-2-(4′-methylphenylethyl)tetrahydrothiophenium bromide in the form of white crystals.

¹H-NMR data (dimethylsulfoxide-d₆, Internal Standard; tetramethylsilane): d(ppm) 2.18-2.30 (m, 4H); 2.42 (s, 3H); 3.48-3.62 (m, 4H); 5.32 (s, 2H); 7.44 (d, 2H, J=8.1 Hz); 7.91 d, 2H, J=8.2 Hz)

(2) 3.05 Parts of sodium salt of 1-adamantylmethyl difluorosulfoacetate obtained in Example 1 (2) was dissolved in 153 parts of acetonitrile. A solution consisting of 2.61 parts of 1-(2-oxo-2-(4′-methylphenylethyl))tethydrothiophenium bromide obtained in (1) above was added to the solution. After stirred for 15 hours, the mixture was concentrated, and extracted with 50 parts of chloroform twice. The organic layers were mixed and washed with ion-exchanged water. The washed organic layer was concentrated. 30 Parts of tert-butyl methyl ether was added to the concentrate, filtered and dried in reduced pressure to obtain 3.44 parts of 1-(2-oxo-2-(4′-methylphenylethyl))tetrahydrothiophenium 1-adamantylmethoxycarbonyldifluoromethanesulfonate in the form of white crystals, which is called as acid generator B3.

¹H-NMR data (dimethylsulfoxide-d₆, Internal Standard: tetramethylsilane): d(ppm) 1.51 (d, 6H);1.63 (dd, 6H); 1.93 (s, 3H); 2.13-2.30 (m, 4H); 2.42 (s, 3H); 3.45-3.64 (m, 4H; 3.81 (s, 2H); 5.28 (s, 2H); 7.43 (d, 2H); 7.91 (d, 2H) Ms (ESI(+) Spectrum): M+221.2 (C₁₃H₁₇OS⁺=221.10) MS (ESI(−) Spectrum): ):M−323.0 (C₁₃H₁₇F₂O₅S⁻32 323.08)

EXAMPLE 4 (Synthesis of 1-(2-oxox-2-(4′-methoxyphenylethyl)tetrahydrothiophenium 1-adamantylmethoxycarbonyldifluoromethanesulfonate)

(1) The reaction and after treatments were conducted in the same manner as in Example 3 (1) except that 50 parts of 2-bromo-4′-methoxyacetophenone was used instead of 50 parts of 2-bromo-4′-methylacetophenone and that the amount of tetrahydrothiophene was 19 parts instead of 21 parts. 63 Parts of 1-(2-oxo-2-(4′-methoxyphenylethyl)tetrahydrothiophenium bromide in the form of white crystals was obtained.

¹H-NMR data (dimethylsulfoxide-d₆, Internal Standard: tetramethylsilane); d(ppm) 2.14-2.34 (m, 4H); 3.48-3.65 (m, 4H); 3.89 (s, 3H); 5.39 (s, 2H); 7.15 (d, 2H, J=8.9 Hz); 8.00 (d, 2H, J=8.9 Hz) (2) The reaction and after treatments were conducted in the same manner as in Example 3 (2) except that 2.61 parts of 1-(2-oxo-2-(4′-methoxyphenylethyl))tetrahydrothiophenium bromide obtained in (1) above was used instead of 2.61 parts of 1-(2-oxo-2-(4′-methylphenylethyl))tetlahydrothiophenium bromide. 3.44 Parts of 1-(2-oxo-2-(4′-methoxyphenylethyl))tetrahydrothiophenium 1-adamantylmethoxycarbonyldifluoromethanesulfonate in the form of white crystals, which is called as acid generator B4, was obtained.

¹H-NMR data (dimethylsulfoxide-d₆, Internal Standard: tetramethylsilane): d(ppm) 1.52 (d, 6H); 1.63 (dd, 6H); 1.93 (s, 3H); 2.12-2.30 (m, 4H); 3.43-3.60 (m, 4H); 3.81 (s, 2H); 3.88 (s, 3H); 5.26 (s, 2H); 7.15 (d, 2H); 7.98 (d, 2H) MS (ESI(+) Spectrum): M+237.2 (C₁₃H₁₇O₂S⁺=237.09) MS (ESI(−) Spectrum): M−323.0 (C₁₃H₁₇F₂O₅S⁻=323.08)

EXAMPLE 5 (Synthesis of 1-(2-oxox-2-(4′-nitrophenylethyl)tetrahydrothiophenium 1-adamantylmethoxycarbonyldifluoromethanesulfonate)

(1) The reaction and after treatments were conducted in the same manner as in Example 3 (1) except that 50 parts of 2-bromo-4′-nitroacetophenone was used instead of 50 parts of 2-bromo-4′-methylacetophenone and that the amount of tetrahydrothiophene was 18 parts instead of 21 parts. 66 Parts of 1-(2-oxo-2-(4′-nitrophenylethyl)tetrahydrothiophenium bromide in the form of white crystals was obtained.

¹H-NMR data (dimethylsulfoxide-d₆, Internal Standard: tetramethylsilane): d(ppm) 2.21-2.29 (m, 4H); 3.59-3.63 (m, 4H); 5.41 (s, 2H); 824 (d, 2H, J=8.9 Hz); 8.45 (d, 2H, J=8.9 Hz)

(2) The reaction and after treatments were conducted in the same manner as in Example 3 (2) except that a solution consisting of 288 parts of 1-(2-oxo-2-(4′nitrophenylethyl)tetrahydrothiophenium bromide obtained in (1) above and 14.4 parts of ion-exchanged water was used instead of the solution consisting of 2.61 parts of 1-(2-oxo-2-(4′-methylphenylethyl)tetrahydrothiophenium bromide and 13.1 parts of ion-exchanged water. 4.26 Parts of 1-(2-oxo-2-(4′-nitrophenylethyl))tetrahydrothiophenium 1-adamantylmethoxycarbonyldifluoromethanesulfonate in the form of white crystals, which is called as acid generator B5, was obtained.

¹H-NMR data (dimethylsulfoxide-d₆, Internal Standard: tetramethylsilane): d(ppm) 1.52 (d, 6H); 1.63 (dd, 6H); 1.93 (s, 3H); 2.18-2.31 (m, 4H); 3.50-3.66 (m, 4H); 3.81 (s, 2H); 5.34 (s, 2H); 8.22 (d, 2H); 8.45 (d, 2H) MS (ESI(+) Spectrum):M+252.0 (C₁₂H₁₄NO₃S⁺=252.07) MS (ESI(−) Spectrum): M−323.0 (C₁₃H₁₇F₂O₅S⁻=323.08)

EXAMPLE 6 (Synthesis of 1-(2-oxo-2-(4′-cyclohexylphenylethyl))tetrahydrothiophenium 1-adamantylmethoxycarbonyldifluoromethanesulfonate)

(1) 50 Parts of 4′-cyclohexylacetophenone was dissolved in 250 parts of chloroform, After cooled to 0° C., 40 parts of bromine was added dropwise thereto. After the reaction, the mixture was washed with 5% aqueous NaHSO₃ solution, with 2% aqueous K₂CO₃ solution and with water, organic layer obtained was concentrated to obtain 60 parts of 2-bromo-4′-cyclohexylacetophenone.

(2) 53 Parts of 2-bromo-4′-cyclohexylacetophenone was dissolved in 265 parts of chloroform, then 17 parts of tetrahydrothiophene was added dropwise thereto. After stirred at room temperature for 24 hours, white solid obtained was filtered, washed with solvent and dried to obtain 44 parts of 1-(2-oxo-2-(4′-cyclohexylphenylethyl))tetrahydrothiophenium bromide in the form of white crystals.

¹H-NMR data (dimethylsulfoxide-d₆, Internal Standard: tetramethylsilane): d(ppm) 1.22-1.52 (m, 5H); 1.70-1.81 (m, 5H); 2.16-2.31 (m, 4H); 2.60-2.67 (m, 1H); 350-3.63 (m, 4H); 539 (s, 2H); 7.47 (d,2H, J=8.3 Hz); 7.94 (d, 2H, J=8.4 Hz)

(3) The reason and after treatments were conducted in the same manner as in Example 3 (2) except that a solution conresisting of 3.15 parts of 1-(2-oxo-2-(4′-cyclohexylphenylethyl))tetrahydrothiophenium bromide obtained in (2) above and 15.7 parts of ion-exchanged water was used instead of the solution conresisting of 2.61 parts of 1-(2-oxo-2-(4′-methylphenylethyl))tetrahydrothiophenium bromide and 13.1 parts of ion-exchanged water. 4.63 Parts of 1-(2-oxo-2-(4′-cyclohexyphenylethyl))tetrahydrothiophenium 1-adamantylmethoxycarbonyldifluoromethanesulfonate in the form of white crystals, which is called as acid generator B6, was obtained.

¹H-NMR data (dimethylsulfoxide-d₆, Internal Standard: tetramethylsilane): d(ppm) 1.22-1.48 (m, 5H); 1.52 (d, 6H); 1.63 (dd, 6H); 1.77-1.81 (m, 5H); 1.93 (s, 3H); 2.18-2.27 (m, 4H); 2.59-2.67 (m, 1H); 3.44-3.63 (m, 4H); 3.81 (s, 2H); 5.28 (s, 2H); 7.48 (d, 2H); 7,92 (d, 2H) MS (ESI(+) Spectrum): M+289.2 (C₁₈H₂₅OS⁺=289.16) MS (ESI(−) Spectrum): M−323.0 (C₁₃H₁₇F₂O₅S⁻=323.08)

EXAMPLE 7 (Synthesis of 1-(2-oxo-2-(4′-phenylphenylethyl))tetrahydrothiophenium 1-adamantylmethoxycarbonyldifluoromethanesulfonate)

(1) The reaction and after treatments were conducted in the same manner as in Example 3 (1) except that 50 parts of 2-bromo-4′-phenylacetophenone was used instead of 50 parts of 2-bromo-4′-methylacetophenone, that 150 parts of acetone and 200 parts of acetonitrile was used instead of 150 parts of acetone, and that the amount of tetrahydrothiophene was 16 parts instead of 21 parts. 58 Parts of 1-(2-oxo-2-(4′-phenylphenylethyl))tetrahydrothiophenium bromide in the form of white crystals was obtained.

¹H-NMR data (dimethylsulfoxide-d₆, Internal Standard: tetramethylsilane): d(ppm) 2.15-2.33 (m, 4H); 3.52-3.65 (m, 4H); 5.40 (s, 2H); 7.44-7.57 (m, 3H); 7.81 (dd, 2H, J=8.4, 1.5 Hz); 7.95 (d, 2H, J=8.4 Hz); 8.10 (d, 2H, J=8.4 Hz)

(2) The reaction and after treatments were conducted in the same manner as in Example 3 (2) except that a solution consisting of 3.15 parts of 1-(2-oxo-2-(4′-phenylphenylethyl))tetrahydrothiophenium bromide obtained in (1) above and 15.7 parts of ion-exchanged water was used instead of the solution consisting of 2.61 parts of 1-(2-oxo-2-(4′-methylphenylethyl))tetrahydrothiophenium bromide and 13.1 parts of ion-exchanged water. 4.63 Parts of 1-(2-oxo-2-(4′-phenylphenylethyl))tetrahydrothiophenium 1-adamantylmethoxycarbonyldifluoromethanesulfonate in the form of white crystals, which is called as acid generator B7, was obtained.

¹H-NMR data (dimethylsulfoxide-d₆, Internal Standard: tetramethylsilane): d(ppm) 1.51 (d, 6H); 1.63 (dd, 6H); 1.92 (s, 3H); 2.20-2.30 (m,4M); 3.48-3.66 (m, 4H); 3.81 (s, 2H); 5.35 (s, 2H); 7.44-7.57 (m, 3H); 7.80 (d, 2H); 7.95 (d, 2H); 8.09 (d, 2H) MS (ESI(+) Spectrum): M+283.2 (C₁₈H₁₉OS⁺=283.12) MS (ESI(−) Spectrum): M−323.0 (C₁₃H₁₇F₂O₅S⁻=323.08)

EXAMPLE 8 (Synthesis of 1-(2-oxo-2-naphtylethyl)tetrahydrothiophenium 1-adamantylmethoxycarbonyldifluoromethanesulfonate)

(1) The reaction and after treatments were conducted in the same manner as in Example 3 (1) except that 75 parts of 2-bromoacetylnaphthalene was used instead of 50 parts of 2-bromo-4′-methylacetophenone, that the amount of acetone and tetrahydrothiophene were 375 parts and 27 parts, respectively, instead of 150 parts and 21 parts. 92 Parts of 1-(2-oxo-2-naphtylethyl)tetrahydrothiophenium bromide in the form of white crystals was obtained.

¹H-NMR data (dimethylsulfoxide-d₆, Internal Standard: tetramethylsilane): d(ppm) 2.20-2.37 (m, 4H); 3.55-3.71 (m, 4H); 5.57 (s, 2H); 7.67-7.79 (m, 2H); 8.00-8.18 (m, 4H); 8.79 (s, 1H)

(2) 5.00 Parts of sodium salt of 1-adamantylmethyl difluorosulfoacetate obtained in Example 1 (2) was dissolved in 50.0 parts of acetonitrile. A solution consisting of 4.71 parts of 1-(2-oxo-2-naphtylethyl)tetrahydrothiophenium bromide obtained in (1) above and 23.6 parts of ion-exchanged water was added to the solution. After stirred for 15 hours, the mixture was concentrated, and extracted first with 100 parts of and second with 50 parts of chloroform. The organic layers were mixed and washed with ion-exchanged water. The washed organic layer was concentrated. 50 Parts of tert-butyl methyl ether was added to the concentrate, filtered and dried in reduced pressure to obtain 6.09 parts of 1-(2-oxo-2-naphtylethyl))tetrahydrothiophenium 1-adamantylmethoxycarbonyldifluoromethanesulfonate in the form of white crystals, which is called as acid generator B8.

¹H-NMR data (dimethylsulfoxide-d₆, Internal Standard: tetramethylsilane): d(ppm) 1.51 (d, 6H); 1.63 (dd, 6H); 1.93 (s, 3H); 2.22-2.31 (m, 4H); 3.53-3.66 (m, 4H); 3.81 (s,2H); 5.46 (s, 2H); 7.67-7.79 (m, 2H); 7.99-8.17 (m, 4H); 8.73 (s, 1H) MS (ESI(+) Spectrum): M+257.0 (C₁₆H₁₇OS⁺=257.10) MS (ESI(−) Spectrum): M−323.0 (C₁₃H₁₇F₂O₅S⁻=323.08)

RESIN SYNTHESIS EXAMPLE 1 (SYNTHESIS OF RESIN A1)

2-Ethyl-2-adamantyl methacxrylate, 3-hydroxy-1-adamantyl methacrylate and α-methacryloyloxyy-γ-butyrolactone were charged at a molar ratio of 5:2.5:2.5 (20.0 parts:9.5 parts:7.3 parts), and methyl isobutyl ketone in twice weight based on all monomers was added, to prepare solution. To the solution was added azobisisobutyronitrile as an initiator in a ratio of 2 mol % based on all monomer molar amount, and the mixture was heated at 80° C. for about 8 hours. Then, the reaction solution was poured into large amount of heptane to cause precipitation, and this operation was repeated three times for purification. As a result, copolymer having a weight-average molecular weight of about 9200 was obtained. This is called resin A1.

EXAMPLES 1 TO 2 AND COMPARATIVE EXAMPLE 1

The following components were nixed and dissolved, further, filtrated through a fluorine resin filter having pore diameter of 0.2 μm, to prepare resist liquid.

<Resin>

resin A1: 10 parts

<Acid generator>

-   -   acid generator B2: 0.69 part

-   -   acid generator B3: 0.709 part

-   -   acid generator C1: 0.659 part

<Quencher>

-   quencher Q1: 2,6-disopropylanile 0.0325 part     <Solvent>

Solvent Y1: propylene glycol monomethyl ether acetate 80.0 parts 2-heptanone 20.0 parts γ-butyrolactone  3.0 parts

Silicon wafers were each coated with “ARC-29A-8”, which is an organic anti-reflective coating composition available from Brewer Co., and then baked under the conditions: 215° C., 60 seconds, to form a 780 Å-thick organic anti-reflective coating. Each of the resist liquids prepared as above was spin-coated over the anti-reflective coating so that the thickness of the resulting film became 0.25 μm after drying, The silicon waders thus coated with the respective resist liquids were each prebaked on a direct hotplate at a temperature of 115° C. for 60 seconds. Using an ArF excimer stepper (“NSR ArF” manufactured by Nikon Corporation, NA=0.55, ⅔ Annular), each wafer thus formed with the respective resist film was subjected to line and space pattern exposure, with the exposure quantity being varied stepwise.

After the exposure, each wafer was subjected to post-exposure baking on a hotplate at a temperature of 115° C. for 60 seconds and then to paddle development for 60 seconds with an aqueous solution of 2.38 wt % tetramethylammonium hydroxide.

Each of a dark field pattern developed on the organic anti-reflective coating substrate after the development was observed with a scanning electron microscope, the results of which are shown in Table 1. The term “dark field pattern”, as used herein, means a pattern obtained by exposure and development through a reticle comprising chromium base surface (light-shielding portion) and linear glass layers (light-transmitting portion) formed in the chromium surface and aligned with each other. Thus, the dark field pattern is such that, after exposure and development, resist layer surrounding the line and space pattern remains on substrate.

Effective Sensitivity (ES):

It is expressed as the amount of exposure that the line pattern (light-shielding layer) and the space pattern (light-transmitting layer) become 1:1 after exposure through 0.13 μm line and space pattern mask and development.

Resolution:

It is expressed as the minimum size of space pattern which gave the space pattern split by the line pattern at the exposure amount of the effective sensitivity.

Profile T/B:

It is expressed by a ratio of top side length (referred to as T) and bottom side length (referred to as B) in line part of 0.13 μm line and space pattern. The closer to 1 the ratio is, the better the profile of its resist pattern is.

Line Edge Roughness (LER):

When line edge roughness is good, its evaluation is marked by “◯”.

When line edge roughness is fair, its evaluation is marked by “Δ”.

When line edge roughness is bad, its evaluation is marked by “X”.

TABLE 1 Acid Resolution No. Generator (μm) Profile T/B ES (mJ/cm²) LER Example 1 B2 0.12 1.00 32.5 ◯ Example 2 B3 0.13 1.00 37.5 ◯ Comparative C1 0.13 0.84 25.0 Δ Example 1 Salt (I) is suitably used for an acid generator capable of providing chemically amplified resist compositions giving patterns having improved line edge roughness and excellent pattern shape and the present resist composition is especially suitably used for an acid generator capable of providing chemically amplified resist compositions for ArF excimer laser lithography, KrF excimer laser lithography and ArF immersion lithography. 

1. A salt of the formula (I):

wherein ring X represents polycyclic hydrocarbon group having tricycle or more and having 10 to 30 carbon atoms, and one or more hydrogen atom in the ring X is optionally substituted with alkyl group having 1 to 6 carbon atoms, alkoxy group having 1 to 6 carbon atoms, perfluoroalkyl group having 1 to 4 carbon atoms or cyano group; Q¹ and Q² each independently represent fluorine atom or perfluoroalkyl group having 1 to 6 carbon atoms; n is an integer of 1 to 12; and A⁺ represents a cation selected from the group consisting of a cation of the following formulae (IIa), (IIb) and (IIc): cation of the formula (IIa):

wherein P¹ and P² each independently represent hydrogen atom, hydroxyl group, alkyl group having 1 to 12 carbon atoms or alkoxy group having 1 to 12 carbon atoms, a cation of the formula (IIb):

wherein P³ and P⁴ each independently represent alkyl group having 1 to 12 carbon atoms or cycloalkyl group having 3 to 12 carbon atoms, or P³ and P⁴ bond to form divalent acyclic hydrocarbon group having 3 to 12 carbon atoms which forms a ring together with the adjacent S⁺, and one or more —CH₂— in the divalent acyclic hydrocarbon group is optionally substituted with —CO—, —O— or —S—, P⁵ represents hydrogen atom, P⁶ represents alkyl group having 1 to 12 carbon atoms, cycloalkyl group having 3 to 12 carbon atoms or aromatic ring group optionally substituted, or P⁵ and P⁶ bond to form divalent acyclic hydrocarbon group which forms 2-oxocycloalkyl together with the adjacent —CHCO—, and one or more —CH₂— in the divalent acyclic hydrocarbon group is optionally substituted with —CO—, —O— or —S—, a cation of the formula (IIc):

wherein P⁷, P⁸, P⁹, P¹⁰, P¹¹, P¹², P¹³, P¹⁴, P¹⁵, P¹⁶, P¹⁷ and P¹⁸ each independently represent hydrogen atom, hydroxyl group, alkyl group having 1 to 12 carbon atoms or alkoxy group having 1 to 12 carbon atoms, B represents sulfur atom or oxygen atom, and m is an integer of 0 or
 1. 2. The salt according to claim 1, wherein each of Q¹ and Q² is independently fluorine atom or trifluoromethyl group.
 3. The salt according to claim 1, wherein the ring X is tricyclic, tetracyclic, pentacyclic or hexacyclic hydrocarbon groups having 10 to 20 carbon atoms.
 4. The salt according to claim 1, wherein the ring X is monovalent residue of a compound of the formula (IIIa) or (IIIb):

wherein X¹ represents (a) alkylene group or (b) oxygen atom, X² represents (a) alkylene group, (b) oxygen atom or (c) no bonding and hydrogen atom in each side, and one or more hydrogen atom in the formulae (IIIa) and (IIIb) is optionally substituted with alkyl group having 1 to 6 carbon atoms, alkoxy group having 1 to 6 carbon atoms, perfluoroalkyl group having 1 to 4 carbon atoms or cyano group.
 5. The salt according to claim 1, wherein A⁺ is a cation of the formula (IId)

wherein P¹⁹ and P²⁰ each independently represent alkyl group having 1 to 6 carbon atoms or cycloalkyl group having 3 to 6 carbon atoms, or P¹⁹ and P²⁰ bond to form divalent acyclic hydrocarbon group having 3 to 6 carbon atoms which forms a ring together with the adjacent S⁺, and one or more —CH₂— in the divalent acyclic hydrocarbon group is optionally substituted with —CO—, —O— or —S—, P²¹ represents hydrogen atom, P²² represents alkyl group having 1 to 6 carbon atoms, cycloalkyl group having 3 to 6 carbon atoms or aromatic ring group optionally substituted, or P²¹ and P²² bond to form divalent acyclic hydrocarbon group which forms 2-oxocycloalkyl together with the adjacent —CHCO—, and one or more —CH₂— in the divalent acyclic hydrocarbon group is optionally substituted with —CO—, —O— or —S—.
 6. The salt according to claim 1, wherein the salt is the one of the formula (IV)

wherein P⁹ and P²⁰ each independently represent alkyl group having 1 to 6 carbon atoms or cycloalkyl group having 3 to 6 carbon atoms, or P¹⁹ and P²⁰ bond to form divalent acyclic hydrocarbon group having 3 to 6 carbon atoms which forms a ring together with the adjacent S⁺, and one or more —CH₂— in the divalent acyclic hydrocarbon group is optionally substituted with —CO—, —O— or —S—, P²¹ represents hydrogen atom, P²² represents alkyl group having 1 to 6 carbon atoms, cycloalkyl group having 3 to 6 carbon atoms or aromatic ring group optionally substituted, or P²¹ and P²² bond to form divalent acyclic hydrocarbon group which forms 2-oxocycloalkyl together with the adjacent —CHCO—, and one or more —CH₂— in the divalent acyclic hydrocarbon group is optionally substituted with —CO—, —O— or —S—.
 7. A process for producing a salt of the formula (I)

wherein ring X represents polycyclic hydrocarbon group having tricycle or more and having 10 to 30 carbon atoms, and one or more hydrogen atom in the ring X is optionally substituted with alkyl group having 1 to 6 carbon atoms, alkoxy group having 1 to 6 carbon atoms, perfluoroalkyl group having 1 to 4 carbon atoms or cyano group; Q¹ and Q² each independently represent fluorine atom or perfluoroalkyl group having 1 to 6 carbon atoms; n is an integer of 1 to 12; and A⁺ represents a cation selected from the group consisting of a cation of the following formulae (IIa), (IIb) and (IIc): a cation of the formula (IIa):

wherein P¹ and P² each independently represent hydrogen atom, hydroxyl group, alkyl group having 1 to 12 carbon atoms or alkoxy group having 1 to 12 carbon atoms, a cation of the formula (IIb):

wherein P³ and P⁴ each independently represent alkyl group having 1 to 12 carbon atoms or cycloalkyl group having 3 to 12 carbon atoms, or P³ and P⁴ bond to form divalent acyclic hydrocarbon group having 3 to 12 carbon atoms which forms a ring together with the adjacent S⁺, and one or more —CH₂— in the divalent acyclic hydrogen group is optionally substituted with —CO—, —O— or —S—, P⁵ represents hydrogen atom, P⁶ represents alkyl group having 1 to 12 carbon atoms, cycloalkyl group having 3 to 12 carbon atoms or aromatic ring group optionally substituted, or P⁵ and P⁶ bond to form divalent acyclic hydrocarbon group which forms 2-oxocycloalkyl together with the adjacent —CHCO—, and one or more —CH₂— in the divalent acyclic hydrocarbon group is optionally substituted with —CO—, —O— or —S—, a cation of the formula (IIc):

wherein P⁷, P⁸, P⁹, P¹⁰, P¹¹, P¹², P¹³, P¹⁴, P¹⁵, P¹⁶, P¹⁷ and P¹⁸ each independently represent hydrogen atom, hydroxyl group, alkyl group having 1 to 12 carbon atoms or alkoxy group having 1 to 12 carbon atoms, B represents sulfur atom or oxygen atom, and m is an integer of 0 or 1; which comprises reacting an ester compound of the formula (V)

wherein M represents Li, Na, K or Ag, and the ring X, Q¹, Q² and n is an integer of 1 to 12, with a compound of the formula (VIII) A⁺ Z⁻  (VIII) wherein Z represents F, Cl, Br, I, BF₄, AsF₆, SbF₆, PF₆ or ClO₄, and A⁺ represents a cation selected from the group consisting of a cation of formulae (IIa), (IIb), and (IIc).
 8. A chemically amplified resist composition comprising a salt of the formula (I):

wherein ring X represents polycyclic hydrocarbon group having tricycle or more and having 10 to 30 carbon atoms, and one or more hydrogen atom in the ring X is optionally substituted with alkyl group having 1 to 6 carbon atoms, alkoxy group having 1 to 6 carbon atoms, perfluoroalkyl group having 1 to 4 carbon atoms or cyano group; Q¹ and Q² each independently represent fluorine atom or perfluoroalkyl group having 1 to 6 carbon atoms; n is an integer of 1 to 12; and A⁺ represents a cation selected from the group consisting of a cation of the following formulae (IIa), (IIb) and (IIc): a cation of the formula (IIa):

wherein P¹ and P² each independently represent hydrogen atom, hydroxyl group, alkyl group having 1 to 12 carbon atoms or alkoxy group having 1 to 12 carbon atoms, a cation of the formula (IIb):

wherein P³ and P⁴ each independently represent alkyl group having 1 to 12 carbon atoms or cycloalkyl group having 3 to 12 carbon atoms, or P³ and P⁴ bond to form divalent acyclic hydrocarbon group having 3 to 12 carbon atoms which forms a ring together with the adjacent S⁺, and one or more —CH₂— in the divalent acyclic hydrocarbon group is optionally substituted with —CO—, —O— or —S—, P⁵ represents hydrogen atom, P⁶ represents allyl group having 1 to 12 carbon atoms, cycloalkyl group having 3 to 12 carbon atoms or aromatic ring group optionally substituted, or P⁵ and P⁶ bond to form divalent acyclic hydrocarbon group which forms 2-oxocycloalkyl together with the adjacent —CHCO—, and one or more —CH₂— in the divalent acyclic hydrocarbon group is optionally substituted with —CO—, —O— or —S—, a cation of the formula (IIc):

wherein P⁷, P⁸, P⁹, P¹⁰, P¹¹, P¹², P¹³, P¹⁴, P¹⁵, P¹⁶, P¹⁷ and P¹⁸ each independently represent hydrogen atom, hydroxyl group, alkyl group having 1 to 12 carbon atoms or alkoxy group having 1 to 12 carbon atoms, B represents sulfur atom or oxygen atom, and m is an integer of 0 or 1, and a resin which is a structural unit having an acid-labile group and which itself is insoluble or poorly soluble in an alkali aqueous solution but becomes soluble in an alkali aqueous solution by the action of an acid.
 9. The composition according to claim 8, wherein the resin contains a structural unit derived from a monomer having a bulky and acid-labile group.
 10. The composition according to claim 9, wherein the bulky and acid-labile group is 2-alkyl-2-adamantyl group or 1-(1-adamantyl)-1-alkylalkyl group.
 11. The composition according to claim 9, wherein the monomer having bulky and acid-labile group is 2-alkyl-2-adamantyl (meth)acrylate, 1-(1-adamantyl)-1-alkylalkyl (meth)acrylate, 2-alkyl-2-adamantyl 5-norbornene-2-carboxylate, 1-(1-adamantyl)-1-alkylalkyl 5-norbornene-2-carboxylate, 2-alkyl-2-adamantyl α-chloroacrylate or 1-(1-adamantyl)-1-alkylalkyl α-chloroacrylate.
 12. The composition according to claim 8, wherein the composition further comprises a basic compound.
 13. The composition according to claim 8, wherein each of Q¹ and Q² is independently fluorine atom or trifluoromethyl group.
 14. The composition according to claim 8, wherein the ring X is tricyclic, tetracyclic, pentacyclic or hexacyclic hydrocarbon groups having 10 to 20 carbon atoms.
 15. The composition according to claim 8, wherein the ring X is monovalent residue of a compound of the formula (IIIa) or (IIIb):

wherein X¹ represents (a) alkylene group or (b) oxygen atom, X² represents (a) alkylene group, (b) oxygen atom or (c) no bonding and hydrogen atom in each side, and one or more hydrogen atom in the formulae (IIIa) and (IIIb) is optionally substituted with alkyl group having 1 to 6 carbon atoms, alkoxy group having 1 to 6 carbon atoms, perfluoroalkyl group having 1 to 4 carbon atoms or cyano group.
 16. The composition according to claim 8, wherein A⁺ is a cation of the formula (IId)

wherein P¹⁹ and P²⁰ each independently represent alkyl group having 1 to 6 carbon atoms or cycloalkyl group having 3 to 6 carbon atoms, or P¹⁹ and P²⁰ bond to form divalent acyclic hydrocarbon group having 3 to 6 carbon atoms which forms a ring together with the adjacent S⁺, and one or more —CH₂— in the divalent acyclic hydrocarbon group is optionally substituted with —CO—, —O— or —S—, P²¹ represents hydrogen atom, P²² represents alkyl group having 1 to 6 carbon atoms, cycloalkyl group having 3 to 6 carbon atoms or aromatic ring group optionally substituted, or P²¹ and P²² bond to form divalent acyclic hydrocarbon group which forms 2-oxocycloalkyl together with the adjacent —CHCO—, and one or more —CH₂— in the divalent acyclic hydrocarbon group is optionally substituted with —CO—, —O— or —S—.
 17. The composition according to claim 8, wherein the salt is the one of the formula (IV)

wherein P¹⁹ and P²⁰ each independently represent alkyl group having 1 to 6 carbon atoms or cycloalkyl group having 3 to 6 carbon atoms, or P¹⁹ and P²⁰ bond to form divalent acyclic hydrocarbon group having 3 to 6 carbon atoms which forms a ring together with the adjacent S⁺, and one or more —CH₂— in the divalent acyclic hydrocarbon group is optionally substituted with —CO—, —O— or —S—, P²¹ represents hydrogen atom, P²² represents alkyl group having 1 to 6 carbon atoms, cycloalkyl group having 3 to 6 carbon atoms or aromatic ring group optionally substituted, or P²¹ and P²² bond to form divalent acyclic hydrocarbon group which forms 2-oxocycloalkyl together with the adjacent —CHCO—, and one or more —CH₂— in the divalent acyclic hydrocarbon group is optionally substituted with —CO—, —O— or —S—. 